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Subaru DCCD Controller – How Does the Controller Work?

In this blog post we talk about the functionality of using an installed DCCDPro Controller. To learn more about DCCD click here. For information on the difference between OEM and Aftermarket DCCD click here. To get help on how to install a DCCD Controller, click here. For tips on which controller to buy, click here.

How does the DCCD in a car work?


The DCCD or Driver Controlled Center Differential refers to the ability to adjust the clutch packs in the center diff to get them to grab or not grab which allows the front and rear wheels to spin at a different rate or not depending on the setting.


When the center diff is open, the clutch packs do not grab each other and can spin freely. This means the front and back wheels can spin at different rates which makes taking tight slow turns easier (IE parking lots). When the center diff is locked, the clutch packs are pushed together so all four wheels must spin at the same rate. People commonly refer to this system in terms of "torque split" but that's not really what is happening. Instead torque split is more a byproduct of center diff slip.


This is where the controller comes in. To activate the DCCD system an electronic input is needed. The DCCD Controller is what handles the adjustment between open and locked for full control of the center diff. Without a controller to tell the center diff what to do, the transmission defaults to open. The byproduct is a 60/40 (70/30 depending on the transmission) torque split with rear wheel drive bias since when power is applied the center diff is allowing for slip. This can add extra wear and tear to your transmission over time which is why we recommend a DCCD Controller for your DCCD equipped transmission.

How does the DCCD Controller work?


Now that we understand what is happening in the car, we can go into more detail about how the controller itself works. Please note that this is specific to the aftermarket DCCD controller of DCCDPro. Stock DCCD and other aftermarket controllers work slightly different in terms of input and logic for output.


Unlike the factory DCCD unit that pulls the wheel speed data from the ABS (Anti-Lock Brake System) and a number of other on board sensors, the Spiider model utilizes the TPS (Throttle Position Sensor) and a G sensor to replicate the information the OEM DCCD controller would get. Using this information combined with built in logic, the DCCDPro will allow for grab or slip to give the driver the most control over the car in any situation.

How Do I Know If The Controller Is Working?


To test if the controller is working we suggest driving to an empty parking lot. Next put the controller in manual and full lock, and turn tightly in a circle. When the center diff is locked, the car will hop because the wheels are all trying to rotate at the same speed. As you go toward open, its going to let the center diff slip and the wheels will go at different rates and the turn will smooth out. As you roll the controller toward lock again it'll feel like it's binding again.



How to Use the Controller:


Turning Controller On/Off

The controller is on when the car is on. Every time the car is turned off and back on again, the Spiider controller will default back to auto mode and where the roller is currently set. The Manual DCCDPro will reset to the position the roller switch is set to. For SI Drive Controls, it will default back to a low lock mode since the roller for the center diff is a toggle.


Display Lights and What They Mean

There are two types of displays for a DCCDPro; the STi gauge cluster or an LED light strip. Both work in similar ways where there is a rainbow of color. Each color dictates what status the controller is in (open vs. locked). Please note the display feature only works with the Spiider Controller WITH CLUSTER OUTPUT and can't be added after the initial purchase.


Auto/Manual: On the stock 02+ STi cluster, it will show auto/manual at the top. On the LED light strip there is a blue light that goes on and off. The blue light on means that the controller is in auto mode, off is in manual mode. For 1993-2000 clusters there isn't an auto position since this feature didn't exist at the time. Use the light on the auto/manual button itself to confirm this setting.


Open vs Closed: Green is open and Red is locked with a number of options in between.




On the DCCDPro, the lights are a live read out so they will move as the controller is adjusting the center diff. When the aftermarket controller is in auto mode, it does not output like the factory unit. On the factory STi, the cluster would not display any lower lights when in auto mode.


The other benefit of an aftermarket controller is that you can still adjust the center diff even in auto mode since the roller switch in auto adjusts aggressiveness (IE more aggressive = tends to not allow for slip for spirited driving and faster cornering at speed). When the roller switch is pushed toward lock it’s more aggressive than when it’s toward open. Since lights are a live readout on the dash, it'll spend more time in the lights near lock when the controller is set at lock and more toward the lights near open when in open.

Common Issues During Install If Controller Is On But Not Adjusting


Parking brake – When the parking brake is engaged, the center diff should be completely open allowing the clutch packs to slip so that the rear wheels can lock up without forcing the front wheels to do the same. If the ebrake light is illuminated on the dash, the DCCDPro’s response is to open the center diff which means the display light will be stuck at open and the lights won't move. The unit can not be tested unless the ebrake or parking brake is down and the ebrake light on the cluster is off. Some cars require the car to be started to turn the parking brake off (due to LEDs and alternator circuitry).


Light on Auto/Manual Button Not Working - When using the OEM auto/manual button, the mode is selected by toggling the switch. When in manual mode the light on the button should turn on. If for some reason the display shows that it is in manual but the light is not working, the light is mostly likely burned out. This can be fixed by replacing the auto/manual button with a new one or checking the forums for the DIY light bulb replacement.


If the lights are bouncing in open or seems like it's acting "funny" - The G-Sensor needs to be calibrated for its position. Just press and hold the auto/manual button with the key off. Turn the key on while continuing to hold the button until the light on the button flashes (2-3 seconds). The G-sensor is re-calibrated for it's current position in the car and should be good to go.


#DCCD #DCCDPro #STIGaugeCluster

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